Low temperature display case



Feb. 25, 1936- c. c. THOMAS ET Al LOW TEMPERATURE DISPLAY CASE Filed Dec. 13, 1950 m m m CHHELES 6'. 77-IOMHS Dar! 6. ELL/s ATTORNEY.

40 bodying this invention Patented Feb. 25, 1936 v 2,032,234 LOW TEMPERATURE DISPLAY CASE Charles C. Thomas an -Mich.,

(1 Don G. Ellis, Detroit, assignors to Kelvinator Corporation,

Detroit, Mich., a corporation of Michigan Application December 13, 1930, Serial No. 502,167

1 Claim.

This invention relates to refrigerated storage and display cases, and more particularly to cases of that type adapted to be refrigerated by mechanical refrigerating apparatus.

5 The principal object of this invention is the.

provision of an inexpensive refrigerated storage and display case adapted to be operated at relatively low temperatures.

Recently a new art of preserving fresh foods has been developed whereby such foods as fresh fruits, vegetables and meats may be preserved indefinitely. This process comprises subjecting the food-to an extremely low temperature so that it will freeze quickly. When so frozen the water contained therein does not separate from the solid matter and form large crystals as is the case when food is frozen slowly. It is these crystals formed in slowly frozen foods that destroy the freshness and flavor of such food by bursting the cell structures thereof. In the quickly frozen foods the water and solid matter are frozen simultaneously and the cell structures remain intact. As long as the quickly frozen foods are kept at a relatively low temperature, generally speaking something below 10 above zero Fahrenheit, they will retain all of their original freshness and flavor. The refrigerated storage and display cases in use heretofore have been of massive and expensive construction and are not adapted to be operated at temperatures low enough for the satisfactory preservation of these so-called quick frozen foods. The development of a widespread use of these foods is therefore being retarded by a lack of suitable merchandising equipment, and due to the excessive cost of the equipment that is available for merchandising this commodity. f

The simplified and inexpensive construction of the refrigerated storage and display case emeliminates one of the obstructions to the development of the quick frozen food industry. However, the lack of suitable merchandising equipment is perhaps an even more serious obstruction to this development.

115 The low temperature cases now in use for preserving normally refrigerated foods could be used for preservingthe frozen foods if it were not for the fact that the refrigerant evaporators em ployed in the present day cases need to be defrosted frequently particularly when operated at extremely low temperatures. During the defrosting process any quick frozen foods which may be disposed within a case employing the conventional type of evaporator would become thawed out. While experiment has shown that 'low temperature case.

all of the freshness and original fiavor of fresh fruits, vegetables, and meats that have been subjected to the quick freezing process will be retained therein as long as they are kept at a relatively low temperature, it has been found that 5 once they become thawed out they must beused within a reasonable time or they will deteriorate just as though they had never been frozen and quite likely in a shorter period of time. Obviously, then, a case which must frequently be 10 subjected to a high enough temperature to defrost the evaporator used therein is not suitable for the preservation of quick frozen foods.

There are several factors which contribute to cause the collection of moisture in the form 15 of frost on a refrigerant evaporator used in a The conventional refrigerant evaporator used in these cases consists either of an elongated tube evaporator or a shorter tube evaporator in the form of a header, with elongated pipe loops associated therewith. Frequently the pipe loops in this type of evaporator are provided with fins secured to the pipe loops at right angles to the axes thereof. In order for an evaporator of this type to refrigerate a display case it must be positioned relatively near the top of the case and operated at a temperature somewhat below that desired in the case in order to establish a temperature diflerential whereby the air within the case is made to circulate about the evaporator. The circulation of air must be practically continuous in order that heat leaking into the case through the walls thereof and through the doors when they are opened may be picked up by the evaporator. It

will be readily apparent that, as a result of constantly passing the air in the case over the evaporator, whatever moisture is contained in the air, over and above the saturation point of air at the temperature at which the evaporator is being op-- erated, will be deposited on the evaporator in the form of frost. As this frost continues to collect on the surface of the evaporator it lowers the evaporators thermal conductivity to such an extent that ultimately it is necessary to defrost the evaporator in order to obtain satisfactory refrigeration. Inasmuch as a low temperature case employing an evaporator which must be defrosted is not suitable for the preservation of quick frozen foods, and since the defrosting of an evaporator is made necessary because of heat leakage and the circulation of air within the case, this invention has as a further object the provision of a refrigerated d splay case'having an evaporator adapted to re- 55 strict the circulation of air therein and to intercept the fiow of heat into the interior of the case.

Because of the fact that it is practically impossible to prevent all circulation of air within a parent, therefore, that it is necessary .to defrost an evaporator employed in a low temperature case even though the circulation of air within the case is greatly restricted, and the leakage of heat into the case is substantially stopped. Since the objection to defrosting the evaporator in a low temperature case is based entirely upon the fact that to do so necessitates raising the temperature of the case suiiiciently to melt the frost on the evaporator, the provision of means not entailing the raising of the temperature of the case for defrosting the evaporator in a low temperature case is essential. This invention therefore has as a still further object the provision of a low temperature refrigerated storage and display case employing an evaporator which is adapted to be defrosted without changing the temperature thereof.

In the drawing:

Figure 1 is a sectional view of the refrigerated storage and display case embodying this invention taken on line 2-2 of Figure 2.

Figure 2 is a plan view of the refrigerated storage and display case shown in Figure 1.

The low temperature case l9 embodying this invention is of exceedingly simple and inexpensive construction having its outer walls formed from a. pair of spaced metallic shells II and i2 with insulating. material I3 disposed therebetween. The case is divided into a display compartment l4 and a storage compartment 5. The front wall l6 of the display compartment ll has its upper extremity inclined toward the rear of the case; This wall is provided with an opening substantially throughout its entire'area which is adapted to receive a window section I! comprising a plurality of spaced parallel plates of glass having their adjacent edges sealed into the wall IE 'to prevent the circulation of air therebetween. The rearv wall ll! of the display compartment ll has its upper extremity inclined toward the front of the case and its lower extremity spaced toward the front of the case from the upper extremity of the rear wall'of the storage compartment IS. The display compartment l4 has a'horizontal top-wall |9 disposed between the upper extremities of the front-and rear walls l1 and I8, and the storage compartment It has a top horizontal'wall 20 disposed between the upper extremity of its rear wall and the lower extremity of the wall I 8. i

The rear wall l8 of the display compartm M and the top wall 29 of the storage compartment i5 are provided with a pluralityr'ofsimilar and adjacent openings adapted to be "closed by doors 2| and 22 respectively. The doors 2| and 22 are of similar construction 'comprising'a plurality of spaced parallel plates of glass 23 having their adjacent edges sealed in insulated door frames 24. Each of the doors 2| and 22 are provided at the opposite extremities of their adjacent edges with corresponding parts 25 of a conventional door hinge. A plurality of rods 26 joining the parts 25 of the hinges together, and 'upon which the doors 2| and 22 may be rotated, are rigidly held in position at the junction of the rear wall-l8 and the horizontal wall 20 by means of stationary hinge portions 21 secured to the. walls. The doors are all provided with handles 28 by means of which theymay be rotated on the rods 26 to an open position.

A definite purpose is served by placing the doors 22 providing access to the interiorof the storage compartment I 5 in a horizontal wall thereof. Due to the well known characteristic of air which causes cold air to seek a lower level than warm air, there will be no circulation through the door opening 22 so long as the air within the storage compartment i5 is colder than the air outside of the case I. Inasmuch as it is contemplated that the interior of the compartment |5 will be maintained at a relatively low temperature there will be a sufiicient difference between the temperature of the air contained therein and the air outside of the case to substantially prevent any loss of the cold air from the case or inflow of warm air into the case.

The-

fact that the door 2| is positioned in a vertical wall of the display compartment M will not cause any particular loss of cold air from that compartment or inflow of warm air into it inasmuch as it is contemplated that this-compartment will be used primarily for display of the contents of the case and all sales will be made from the contents of the storage compartment IS.

The display compartment I4 is separated from the storage compartment l5 by a partition 30 comprising a continuation of the inner metallic shell l2 and a metal sheet 3| spaced from the inner shell |2 and having its edges at its opposite ends and at one side sealed to the adjacent edges of the inner shell l2 as indicated at 32. The

edge on the opposite side of the metal sheet 3| is sealed to the front wall of the storage .com-

partment l5 as indicated at 33.

with the high side of a. refrigerant condensing i,

unit, not shown, and its other extremity in communication with the low side of the same unit.

- Suitable well known means, not shown, are em-* ployed for the purpose of admitting refrigerant to the evaporator coil 29 and for causing the condensing unitto operate in response to temperature variations within the case l0.

A portion of the refrigerant conduit forming the evaporator coil 29 is sealed within the vertical walls of the storage compartment l5 anddisposed between the insulating material l3 and the inner metallic shell l2; The remainder of the refrigerant conduit forming the evaporator coil 29 is concealed within the partition 39 separating the display compartment II from the storage compartment |5. That part of the refrigerant evaporator coil 29 disposed within the vertical walls of the storage compartment I5 is preferably in direct metallic contact with the inner shell l2, and that portion of theevaporator 29 disposed within the partition 39 is preferably in contact with the metallic plate 3|.

The space between the metallic plate ll and the inner shell I2 and between, the insulation material l3 and the inner shell |2 which surrounds-theevaporator coil 29 is filled with any suitable holdover means 34 of good conductivity. While the holdover means illustrated in-the drawing consists of a cementcomposition which is plastic when first mixed, so that it may be poured into the space that it is to occupy, and hardens quickly, it should be understood that the purposes of this invention may be served equally well by. any other holdover means of good conductivity.

The partition is adapted to support the con tents of the display compartment I4. The evaporator embedded in the partition 30 cools these contents by means of conduction. The food contained in this compartment will therefore be preserved at a proper temperature even though a considerable amount of heat should leak through the sloping vertical walls or the horizontal top wall of this compartment. Normally if a solid substance of very low temperature comes in contact with warm air, ice crystal will be deposited on its surface. This will not happen to articles of food in the display compartment even if a relatively large amount of heat leaks into it because the food is itself a conductor of heat, and being in direct thermal contact with the evaporator coil will extract the heat from the air immediately adjacent it on all sides. There will therefore be what might be called a layer of cold ,air immediately above the food in this compartment. v

The contents of the storage compartment 15 are supported by the bottom wall thereof and by a plurality of shelves provided with wheels 36 adapted to support the shelves upon tracks 31 extending from the front to the rear wall of the compartment l5. It is contemplated that sales of merchandise selected by a purchaser from the display in the compartment M will be made from the contents of the trays 35 in the compartment l5. These trays are approximately one half of the length of the tracks '31 and may be pushed forward into the position shown in the dotted lines in Figure 1, to permitthe user of the case In to withdraw the merchandise disposed beneath the trays and replenish the supplies Icarried by the trays when necessary. This arrangemerit permits the utilization of practically the entire space in the storage'compartment I5 while at the same time providing for the read accessibility of the contents of that compartment.

Since the door 22 providing access to the interior of the storage compartment is positioned in a horizontal'wall-thereof, and consequently restricts the circulation of air therethrough, and since the evaporator coil 29 is positioned in the vertical walls of the compartment l5'where it will intercept and absorb the heat leaking through the walls, it is apparent that there will be no particular circulation of air within the compartment l5 and that the contents thereof will be cooled by radiation and conduction.

Even though there is no particular circulation of air in the compartment I 5 there will'nevertheless be deposited on the inner metallic shell l2 a certain amount of frost representing moisture taken from the air adjacent the walls of the compartment. While this frost will not be enough to interfere particularly with the cooling of the compartment, it will undoubtedly accumulate to such extent as to require its removal from time to time. This can be done simply by scraping the frost oil the metallic shell I2 and without materially changing the temperature of the compartment l5. Likewise although the circulation of air within the compartment I! will be very limited, there will obviously be a deposit of frost on the plate 3|. This may also be. removed without substantially changing the temperature of that compartment by scraping the plate. It will thus be apparent that relatively low temperatures may be maintained in both the display compartment I4 an the storage compartment l5 continuously for an an indefinite period of time.

We claim:

A unitary refrigerated show and storage case for low temperature refrigeration'comprising a cabinet having heat insulating walls, the upper portion of the cabinet walls being transparent for display p poses, an insulated door providing access to the display portion of the cabinet, an impervious refrigerated floor for the display portion forming the ceiling for the lower portion, additional refrigerating means embedded in the lower insulated walls, said lower portion providing a storage compartment for storing a supply of the food displayed, an insulated door providingaccess to the storage compartment and a smooth inner lining thermally associated with said refrigerating means whereby frost may be conveniently removed.

. CHARLES C. THOMAS.

DON G. ELLIS. 

